Solid-oxide shaped fuel cell module

ABSTRACT

There is provided a solid oxide fuel cell module comprising a substrate with an internal fuel flow part provided therein, at least a face thereof, in contact with cells, and interconnectors, being an insulator, a plurality of the cells each comprised of an anode, an electrolyte, and a cathode, stacked in sequence, formed on a surface of the substrate, and the interconnectors each electrically connecting in series the cells adjacent to each other, wherein the respective cells are varied in area along the direction of fuel flow, and solid oxide fuel cell bundled modules using the same. With the solid oxide fuel cell module of a multi-segment type, according to the invention, it is possible to aim at higher voltage, and to attain improvement in power generation efficiency, and current collecting efficiency.

TECHNICAL FIELD

The invention relates to a solid oxide fuel cell module, and morespecifically, to a solid oxide fuel cell module comprising a multitudeof cells disposed on a surface of a substrate with an internal fuel flowpart provided therein, at least a face of the surface, in contact withthe cells, and interconnectors, being an insulator, and solid oxide fuelcell bundled modules (that is, a set of solid oxide fuel cell modules,comprised of a plurality of units of the solid oxide fuel cell modulesthat are coupled up).

BACKGROUND TECHNOLOGY

A solid oxide fuel cell (referred to hereinafter merely as an SOFC whereappropriate) is a fuel cell using an oxide as a solid electrolyticmaterial having ionic conductivity. The fuel cell generally has anoperating temperature as high as on the order of 1000° C., but there islately being developed one having an operating temperature not higherthan about 800° C., for example, on the order of 750° C. With the SOFC,there are disposed an anode (that is, a fuel electrode), and a cathode(that is, an air electrode or an oxygen electrode) with an electrolyticmaterial sandwiched therebetween, thereby making up a single cell as athree-layer unit of the anode/an electrolyte/the cathode.

When the SOFC is operated, fuel is fed to the anode side of the singlecell (also referred to merely as “a cell” where appropriate in thepresent description), air as an oxidizing agent is fed to the cathodeside thereof, and electric power is obtained by connecting both theelectrodes to an external load. However, with the single cell of oneunit only, a voltage only on the order of 0.7V at most can be obtained,so that there is the need for connecting in series a plurality of thesingle cells together in order to obtain electric power for practicaluse. For the purpose of electrically connecting adjacent cells with eachother while concurrently feeding fuel, and air to the anode, and thecathode, respectively, after properly distributing them, andsubsequently, effecting emission thereof, separators (=interconnectors)and the single cells are alternately stacked.

Such an SOFC system as described above is a type wherein a plurality ofthe single cells are stacked one on top of another, but it isconceivable to adopt a multi-segment type in place of such a type asdescribed, for example, in Fifth European Solid Oxide Fuel Cell forum(1-5, Jul., 2002) p. 1075-, the external appearance of the multi-segmenttype and so forth are disclosed although the contents thereof are notnecessarily clear-cut in detail. As the multi-segment type, two typesincluding a cylindrical type and a hollow flat type are conceivable.

FIG. 1 is a view showing an example of the structure of the hollow flattype of the two types, FIG. 1(a) being a perspective squint view, FIG.1(b) a plan view, and FIG. 1(c) a sectional view taken on line A-A inFIG. 1(b). As shown in FIGS. 1(a)-(c), there are formed a plurality ofcells 2 each made up by stacking an anode 3, an electrolyte 4, and acathode 5 in that order on an insulator substrate 1 in a hollow flatsectional shape, and the respective cells 2 are structured so as to beelectrically connected in series with each other through theintermediary of an interconnector 6, respectively. Fuel is caused toflow in space within the insulator substrate 1, that is, an internalfuel flow part 7, in parallel with a lineup of the cells 2, as indicatedby an arrow (→) in FIGS. 1(a) and 1(c).

Now, with the SOFC system of the hollow flat type as described above,the fuel is going to become thinner as it moves in the direction of itsflow. Nevertheless, since the respective cells are disposed so as to beelectrically connected in series, the same current is forced to flowbetween the cells even under thinned fuel. Consequently, voltage dropincreases, thereby causing a problem of lower power generationefficiency. In addition, since the respective cells are connected inseries in one direction, a voltage obtained is limited.

DISCLOSURE OF THE INVENTION

Under the circumstances, it is an object of the invention to aim athigher voltage by solving the various problems occurring to an SOFCsystem of a multi-segment type, and to provide a solid oxide fuel cellmodule, and solid oxide fuel cell bundled modules, attaining improvementin power generation efficiency, and current collecting efficiency,

The invention provides (1) a solid oxide fuel cell module comprising:

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow.

The invention provides (2) a solid oxide fuel cell module comprising:

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed in each of a plurality of rowsfrom first to n-th rows on a surface of the substrate; and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow.

The invention provides (3) solid oxide fuel cell bundled modulescomprising:

two units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

the respective modules being provided with a female-threaded hole, onone-side faces thereof, opposing each other, on the fuel inlet sidethereof, and an interval retaining hollow member having a skirting partprovided with external threads so as to mate with the respectivefemale-threaded holes adjacent thereto being interposed between thefemale-threaded holes, wherein said two units of the solid oxide fuelcell modules are securely held with each other by rotativelyreciprocating the interval retaining hollow member.

The invention provides (4) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed in such a way asto be plane parallel with each other to be coupled together,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

two modules at both extreme ends, respectively, among said plural unitsof the solid oxide fuel cell modules, being provided with afemale-threaded hole, on one-side faces thereof, on the fuel inlet sidethereof, while the respective modules between the two modules at boththe extreme ends, respectively, being provided a female-threaded hole,on both-side faces thereof, on the fuel inlet side thereof, and aninterval retaining hollow member having a skirting part provided withexternal threads so as to mate with the respective female-threaded holesadjacent thereto being interposed between the female-threaded holesadjacent to each other, wherein the respective solid oxide fuel cellmodules are securely held with each other by rotatively reciprocatingthe respective interval retaining hollow members.

The invention provides (5) solid oxide fuel cell bundled modulescomprising:

two units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

the respective modules being provided with an opening, on one-side facesthereof, opposite to each other, on the fuel inlet side thereof, andalso a hole corresponding to the diameter of the shank of a screw bolton the other side faces thereof, opposite from the openings of therespective modules, while an interval retaining hollow member having askirting part corresponding to the respective openings being interposedbetween the openings, wherein said two units of the solid oxide fuelcell modules are securely held with each other by inserting the screwbolt with a head at one end thereof, or the screw bolt with threads atboth ends thereof into the holes, openings, and a hollow part of theinterval retaining hollow member, from one end of the screw bolt, andtightening up with a nut, or nuts.

The invention provides (6) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

two modules at both the extreme ends, respectively, among said pluralunits of the solid oxide fuel cell modules, being provided with anopening, on one-side faces thereof, on the fuel inlet side thereof, andalso a hole corresponding to the diameter of the shank of a screw bolton the other side faces thereof, opposite from the respective openingsof the two modules at both the extreme ends, respectively, while therespective modules between the two modules at both the extreme ends,respectively, being provided an opening, on both-side faces thereof, onthe fuel inlet side thereof, and an interval retaining hollow memberhaving a skirting part provided with external threads so as to mate withthe respective openings adjacent thereto being interposed between theadjacent openings, wherein the respective solid oxide fuel cell modulesare securely held with each other by inserting the screw bolt with ahead at one end thereof, or the screw bolt with threads at both endsthereof into the holes, openings, and a hollow part of the intervalretaining hollow member, from one end of the screw bolt, and tighteningup with a nut, or nuts.

The invention provides (7) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

two modules at both the extreme ends, respectively, among said pluralunits of the solid oxide fuel cell modules, being provided with anopening, on one-side faces thereof, on the fuel inlet side thereof whilethe respective modules between the two modules at both the extreme ends,respectively, being provided an opening, on both-side faces thereof, onthe fuel inlet side thereof, and an interval retaining hollow memberhaving a skirting part matching the respective openings adjacent theretobeing interposed between the adjacent openings, wherein the solid oxidefuel cell modules in whole are disposed inside a casing to be securelyheld with each other,

The invention provides (8) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

the module of said plural units of the solid oxide fuel cell modules, atthe forefront in the direction of the fuel flow, being provided with anopening on the fuel feeding side thereof while the respective modulessubsequent to the module at the forefront being provided openings on thespent fuel emission and fuel feeding sides thereof, respectively, and aninterval retaining hollow member having a skirting part being interposedbetween the openings of the respective modules adjacent to each other,opposite to each other, wherein the solid oxide fuel cell modules inwhole are disposed inside a casing to be securely held with each other,

The invention provides (9) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

the module of said plural units of the solid oxide fuel cell modules, atthe forefront in the direction of the fuel flow, being provided with anopening on the fuel feeding side thereof while the respective modulessubsequent to the module at the forefront being provided openings on thespent fuel emission and fuel feeding sides thereof, respectively, and aninterval retaining hollow member having a skirting part, and an intervalretaining unhollow member having a skirting part being interposedbetween the openings of the respective modules adjacent to each other,opposite to each other, in the upper part and lower part of therespective modules, in a staggered fashion, wherein the solid oxide fuelcell modules in whole are disposed inside a casing to be securely heldwith each other,

The invention provides (10) solid oxide fuel cell bundled modulescomprising:

plural units of solid oxide fuel cell modules disposed with an intervalprovided therebetween, and in such a way as to be plane parallel witheach other,

said solid oxide fuel cell module comprising;

a substrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator;

a plurality of the cells each comprised of an anode, an electrolyte, anda cathode, stacked in sequence, formed on a surface of the substrate;and

the interconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow,

two modules at both the extreme ends, respectively, among said pluralunits of the solid oxide fuel cell modules, being provided with anopening, on one-side faces thereof, on the fuel inlet side thereof,while the respective modules between the two modules at both the extremeends, respectively, being provided an opening, on both-side facesthereof, on the fuel inlet side thereof, and an interval retaininghollow member having a skirting part matching the respective openingsadjacent thereto being interposed between the adjacent openings, whereinthe solid oxide fuel cell modules in whole are disposed inside a casingto be securely held with each other, and are structured such thatpressure loss occurs at parts of the respective modules, where fuelinside the respective modules is released to outside.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(a) to 1(c) are views showing an example of the structure of ahollow flat type solid oxide fuel cell module;

FIGS. 2(a) to 2(c) are views showing Working Example 1 of an SOFC modulestructure according to the invention;

FIGS. 3(a) to 3(g) are views showing examples of the structure of “asubstrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator”;

FIGS. 4(a) to 4(c) are views showing examples of the structure of “asubstrate with an internal fuel flow part provided therein, at least aface thereof, in contact with cells, and interconnectors, being aninsulator”;

FIGS. 5(a) and 5(b) are views showing examples of the structure of asubstrate, at least a face thereof, in contact with cells, being aninsulator;

FIGS. 6(a) to 6(c) are views showing Working Example 2 of an SOFC modulestructure according to the invention;

FIGS. 7(a), 7(b), and FIGS. 8(a), 8(b) are views showing severalexamples of structure modes, respectively, in which cells disposed inrespective rows of an SOFC module are varied in area along the directionof fuel flow by the row;

FIGS. 9(a) to 9(c) are views showing Working Example 1 of a structurefor coupling up the SOFC modules according to the invention;

FIGS. 10(a), and 10(b) are views showing Working Example 2 of astructure for coupling up the SOFC modules according to the invention;

FIGS. 11(a) to 11D, and FIGS. 12(a), 12(b) are views showing WorkingExample 3 of a structure for coupling up the SOFC modules according tothe invention;

FIGS. 13(a), and 13(b) are views showing Working Example 4 of astructure for coupling up the SOFC modules according to the invention;

FIG. 14, FIGS. 15(a), and 15(b) are views showing Working Example 5 of astructure for coupling up the SOFC modules according to the invention;

FIGS. 16(a) and 16(b) are views showing Working Example 6 of a structurefor coupling up the SOFC modules according to the invention;

FIGS. 17(a) to 17(c) are views showing Working Example 7 of a structurefor coupling up the SOFC modules according to the invention;

FIGS. 18 and 19 are views showing the Working Example 8 of a structurefor coupling up the SOFC modules according to the invention,respectively;

FIG. 20 is a view showing an example of a construction for configurationof conductors for drawing out current.

FIG. 21 is a view showing an interconnector configuration construction 1according to the invention;

FIG. 22 is a view showing an interconnector configuration construction 2according to the invention;

FIG. 23 is a view showing an interconnector configuration construction 3according to the invention;

FIG. 24 is a view showing an interconnector configuration construction 4according to the invention;

FIG. 25 is a view showing an interconnector configuration construction 5according to the invention;

FIG. 26 is a view showing an interconnector configuration construction 6according to the invention;

FIG. 27 is a view showing an interconnector configuration construction 7according to the invention;

FIG. 28 is a view showing an interconnector configuration construction 8according to the invention;

FIG. 29 is a view showing an interconnector configuration construction 9according to the invention;

FIG. 30 is a view showing an interconnector configuration construction10 according to the invention; and

FIG. 31 is a view showing an interconnector configuration construction11 according to the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is concerned with an SOFC module comprising aplurality of cells each made up of an anode, an electrolyte, and acathode sequentially formed on a surface of a substrate with an internalfuel flow part provided therein, at least a face of the substrate, incontact with the cells, and interconnectors, being an insulator, and thecells adjacent to each other being electrically connected in seriesthrough the intermediary of the respective interconnectors, and is alsoconcerned with a set of the SOFC modules, made up by coupling up aplurality of the SOFC modules, that is, SOFC bundled modules. Further,the invention has a basic feature in that the respective cells arevaried in area along the direction of fuel flow.

With the SOFC module of a multi-segment type, according to theinvention, it is possible to aim at higher voltage, and to attainimprovement in power generation efficiency, and current collectingefficiency.

The substrate with the internal fuel flow part provided therein, atleast the face thereof, in contact with the cells, and theinterconnectors, being the insulator, may be of any structure providedthat fuel can be distributed therein, a plurality of the cells can bedisposed on an outer surface thereof, and at least a face thereof, incontact with the cells and the interconnectors, is an insulator, and thestructure thereof may be, for example, rectangular (hollow-flat),polygonal, such as triangular, quadrilateral (hollow-quadrilateral),pentagonal, and so forth, circular, elliptical, and of other suitableshapes, in a cross-sectional shape. Besides the case where one unit ofthe internal fuel flow part is provided inside the insulator substrate,a plurality of units of the internal fuel flow parts can be providedtherein.

As the constituent material of a solid electrolyte, use may be of anysolid electrolytic material having ionic conductivity, and as examplesof the constituent material, there can be included materials describedunder items (1) to (4) given hereunder:

-   -   (1) yttria stabilized zirconia [YSZ: (Y₂O₃)_(x)(ZrO₂)_(1-x)] (in        chemical formula, x=0.05 to 0.15);    -   (2) scandia stabilized zirconia [(Sc₂O₃)_(x)(ZrO₂)_(1-x)] (in        chemical formula, x=0.05 to 0.15);    -   (3) yttria doped ceria [(Y₂O₃)_(x)(CeO₂)_(1-x)] (in chemical        formula, x=0.02 to 0.4);    -   (4) gadolinia doped ceria [(Gd₂O₃)_(x)(CeO₂)_(1-x)] (in chemical        formula, x=0.02 to 0.4)

As the constituent material of the anode, use is made of, for example,material composed mainly of Ni, material composed of a mixture of Ni andYSZ [(Y₂O₃)_(x)(ZrO₂)_(1-x)] (in chemical formula, x=0.05 to 0.15), andso forth. In the case of the material composed of the mixture of Ni andYSZ, the material with not less than 40 vol. % of Ni diffused in themixture is preferably used.

As the constituent material of the cathode, use is made of, for example,Sr doped LaMnO₃.

As the constituent material of the substrate with the internal fuel flowpart provided therein, at least the face thereof, in contact with thecells, and the interconnectors, being the insulator, use can be made ofa mixture of MgO, and MgAl₂O₄, a zirconia based oxide, a mixture of thezirconia based oxide, MgO, and MgAl₂O₄, and so forth. Among thosematerials, the mixture of MgO and MgAl₂O₄ is preferably a mixture of MgOand MgAl₂O₄ containing 20 to 70 vol. % of MgO. Further, as an example ofthe zirconia based oxide, there can be cited an yttria stabilizedzirconia [YSZ: (Y₂O₃)_(x) (ZrO₂)_(1-x)] (in chemical formula, x=0.03 to0.12), and so forth.

With the SOFC module according to the invention, the interconnectorconnects the anode to the cathode between the respective cells adjacentto each other (that is, between the anodes of the respective cells andthe cathodes of the respective cells disposed next to the former). Asexamples of the constituent material of the interconnector, there can becited materials described under items (1) to (4) given hereunder:

-   -   (1) material composed mainly of an oxide, expressed by chemical        formula (Ln, A) CrO₃ (in chemical formula, Ln refers to        lanthanoids, and A refers to Ba, Ca, Mg, or Sr)    -   (2) an oxide containing Ti, for example, MTiO₃ (in chemical        formula, M refers to at least one element selected from the        group consisting of Ba, Ca, Pb, Bi, Cu, Sr, La, Li, and Ce)    -   (3) material composed mainly of Ag. In the case of this        material, it is desirable to cover an interconnector made of        this material with glass.    -   (4) material composed of one substance or not less than two        substances, selected from the group consisting of Ag, Ag solder,        and a mixture of Ag and glass.

Further, the SOFC module according to the invention may comprise aninterface layer between the electrolyte and the cathode.

SPECIFIC MODES OF THE INVENTION

Specific modes of the invention are sequentially described hereinafter,however, it goes without saying that the invention is not limitedthereto.

WORKING EXAMPLE 1 OF AN SOFC MODULE STRUCTURE

FIGS. 2(a) to 2(c) are views showing Working Example 1 of an SOFC modulestructure according to the invention. FIG. 2(a) is a perspective squintview, FIG. 2(b) a plan view, and FIG. 2(c) a sectional view taken online A-A in FIG. 2(b), showing the SOFC module structure as expanded soas to be larger than that in FIG. 2(b). As shown in FIGS. 2(a) to 2(c),on either the upper side face or the underside face, or both the facesof a porous insulator substrate 11 in a hollow-flat sectional shape,with an internal fuel flow part 17 provided therein, at least the facethereof, in contact with cells, and interconnectors, being an insulator,there are formed in series a plurality of the cells 12 each made up ofan anode 13, an electrolyte 14, and a cathode 15′, 15″ or 15′″, stackedin sequence, and the cells 12 adjacent to each other are connected witheach other through the intermediary of the respective interconnectors16. In FIG. 2(c), the interconnector 16 is seen covering part of thesurface of the cathode 15, however, may cover the entire surfacethereof. Further, in FIG. 2(c), blank portions indicated by S may befilled up with the interconnector material. In those respects described,the same applies to Working Examples that will be described hereinafter.

Then, the SOFC module is structured such that the respective cells arevaried in area along the direction of fuel flow. In FIGS. 2(a) to 2(c),there is shown one case where the respective cells sequentially increasein area along the direction of the fuel flow, as indicated by an arrow(→Z), and as indicated by 15′, 15″. 15′″ in FIG. 2(c), the cathodes arestructured so as to sequentially increase in area as the anode 13, andthe electrolyte 14 sequentially increase in area along the direction ofthe fuel flow.

Besides the above, as examples of modes, wherein the respective cellsare structured so as to vary in area along the direction of the fuelflow, the SOFC module may be structured as described under items (1) to(3) given hereunder:

-   -   (1) One cell group is made up of a plurality of the cells        identical in area.

The SOFC module is structured such that there are sequentially disposedthe cell groups with the respective cells thereof, sequentiallyincreasing in area along the direction of the fuel flow. For example,there are disposed the respective cell groups in sequential order, suchas the cell group a→the cell group b→the cell group c . . . along thedirection of the fuel flow, in which case, the areas of the respectivecells of the cell group b are larger than those of the cell group a, theareas of the respective cells of the cell group c are larger than thoseof the cell group b, and so on.

-   -   (2) One cell group is made up of a plurality of the cells        identical in area.

The SOFC module is structured such that there are sequentially, andalternately disposed the cell groups, and the cells not belonging to anyof the cell groups (that is, individual cells) along the direction ofthe fuel flow while the areas of the respective cells are sequentiallyincreased. For example, there are disposed the respective cell groupsand the individual cells in a manner, such as the cell group a→the cellb→the cell group c→the cell d . . . along the direction of the fuelflow, in which case, the area of the cell b is larger than the areas ofthe respective cells of the cell group a, the areas of the respectivecells of the cell group c are larger than the area of the cell b, and soon.

-   -   (3) One cell group is made up of a plurality of the cells        identical in area.

The SOFC module is structured such that there are disposed the cellgroups, and the cells not belonging to any of the cell groups (that is,individual cells) sequentially along the direction of the fuel flow, butat random, while the areas of the respective cells are sequentiallyincreased along the direction of the fuel flow. For example, therespective cell groups, and the individual cells are disposed in amanner, such as the cell group a→the cell b→the cell c→the cell groupd→the cell e . . . along the direction of the fuel flow, in which case,the area of the cell b is larger than the areas of the respective cellsof the cell group a, the area of the cell c is rendered larger than thatof the cell b, the areas of the respective cells of the cell group d arelarger than that of the cell c, and so on.

Electric power is drawn out between the cell at the forefront in thedirection of the fuel flow and the cell at the rearmost in the directionof the fuel flow. As fuel is consumed at the respective cells, itbecomes gradually thinner along the direction of the fuel flow, however,in the case of Working Example 1 as shown in FIGS. 2(a) to 2(c), theareas of the respective cells are sequentially increased, so thatcurrent density sequentially decreases. In this respect, the sameapplies to the cases of the examples of the modes described under items(1) to (3) as above. Accordingly, power generation efficiency can beenhanced. Further, since there is an increase in the number of the cellsof which adjacent ones are electrically connected in series, voltageincreases, and conversion efficiency from direct current (DC) toalternating current (AC) can be enhanced.

The substrate with the internal fuel flow part provided therein, atleast the face thereof, in contact with the cells, and theinterconnectors, being the insulator, may be of any structure providedthat fuel can be distributed internally, and the plurality of the cellscan be disposed on the outer surface thereof. FIGS. 3(a) to 3(g) areviews showing some examples of the substrate. In those figures, parts incommon with those in FIGS. 3(a) to 3(c), respectively, are denoted bylike reference numerals. FIG. 3(a) shows an example of the porousinsulator substrate rectangular or flat, in cross-section, showing thecase of the insulator substrate 11 provided with one hollow region. Thehollow region functions as a fuel flow path, that is, the internal fuelflow part 17. FIGS. 3(b) to 3(e) are views showing examples of theporous insulator substrate rectangular or flat, in cross-section,respectively, showing the cases of the respective insulator substratesprovided with a plurality of hollow regions, that is, a plurality of theinternal fuel flow parts 17. FIGS. 3(f) and 3(g) are views showingexamples of the porous insulator substrate circular or elliptical, incross-section, respectively, showing the cases of the respectiveinsulator substrates 11 provided with a plurality of fuel flow paths,that is, a plurality of the internal fuel flow parts 17. With theexamples shown in FIGS. 3(b) to 3(g), respectively, the cross-sectionalshape of the internal fuel flow part 17 is not limited to the respectiveshapes shown in those figures, and may be other appropriate shape.

FIGS. 4(a) to 4(c) are views showing the substrate structured to be inshape quadrilateral or substantially quadrilateral in cross-section,respectively. In those figures, parts in common with those in FIGS. 3(a)to 3(g), respectively, are denoted by like reference numerals. With anexample shown in FIG. 4(a), an anode 13 is disposed on both an upperside face, and an underside face of an insulator substrate 11, and anelectrolyte 14 is disposed on the entire peripheral surface of theinsulator substrate 11, including the anodes 13. Then, a cathode 15 isdisposed on portions of the surface of the electrolyte 14, correspondingto the respective anode 13, on the upper side and the underside. With anexample shown in FIG. 4(b), an anode 13 is disposed on the entireperipheral surface of an insulator substrate 11, and an electrolyte 14is disposed on the entire peripheral surface of the anode 13. Then, acathode 15 is disposed on portions of the surface of the electrolyte 14,on the upper side, and underside, respectively. With an example shown inFIG. 4(c), an anode 13 is disposed on the entire peripheral surface ofan insulator substrate 11, and an electrolyte 14 is disposed on theentire peripheral surface of the anode 13. Then, a cathode 15 isdisposed on portions of the surface of the electrolyte 14, on the upperside, and underside, respectively, and a cathode 15 or an electricconductor 18 is disposed on portions of the surface of the electrolyte14, other than the portions of the surface thereof, where the respectivecathodes 15 are disposed. In FIGS. 4(a) to 4(c), there are shown thecases of the substrate quadrilateral or substantially quadrilateral incross-section, however, the same applies to the cases of the substrateother than that in cross-section, such as other polygonal, elliptical,and so forth, in cross-section. In other respects, the substrate is thesame in structure as that shown in FIGS. 2 and 3.

Structure of the Substrate

With the invention, for the substrate, use is made of a substrate withan internal fuel flow part provided therein, at least the face thereof,in contact with the cells, and the interconnectors, being a porousinsulator. FIGS. 5(a) and 5(b) are views showing examples of thestructure of the substrate, at least the face thereof, in contact withthe cells, being an insulator. In those figures, parts in common withthose in FIGS. 4(a) and 4(b), respectively, are denoted by likereference numerals. With the example of the structure, shown in FIG.5(a), portions of the substrate, in contact with respective anodes 13,are made up of a porous insulator 11 while other portions thereof ismade up of an electrically conductive substance (conductive substance)18. In this respect, the same applies to the case of the substrate ofwhich at least a face, in contact with the interconnectors, is aninsulator. With the example of the structure, shown in FIG. 5(b), thereis shown the case where the substrate in whole, including the facesthereof, in contact with the cells, is made up of the porous insulator11. In this respect, the same applies to the case of the substrate ofwhich at least the face, in contact with the interconnectors, is aninsulator. In FIGS. 5(a) and 5(b), there are shown the cases of thesubstrate rectangular in cross-section, however, the same applies to thecases of the substrate other than that in cross-section, such as otherpolygonal, elliptical, circular, and so forth, in cross-section. As forthe structure of the substrate, the same applies to Working Example 2 ofan SOFC module structure, according to the invention, as describedhereinafter.

WORKING EXAMPLE 2 OF THE SOFC MODULE STRUCTURE

FIGS. 6(a) to 6(c) are views showing Working Example 2 of the SOFCmodule structure, according to the invention. FIG. 6(a) is a perspectivesquint view, FIG. 6(b) a plan view, and FIG. 6(c) a sectional view takenon line A-A in FIG. 6(b), showing the SOFC module structure as expandedso as to be larger than that in FIG. 6(b). As shown in FIGS. 6(a) to6(c), in each of a plurality of rows from first to n-th rows, on eitherthe upper side face or the underside face, or both the faces of aninsulator substrate rectangular or hollow-flat, in cross-sectionalshape, there are formed a plurality of cells 12 each made up of an anode13, an electrolyte 14, and a cathode 15, stacked in sequence, and thecells 12 adjacent to each other are electrically connected in seriesthrough the intermediary of respective interconnectors. In FIGS. 6(a) to6(c), there is shown the case of two rows of the first and second rows,however, the same applies to the case of three or more rows. In FIG.6(a), there is shown the direction of current flow between the cells onthe top face (surface) of the SOFC module, however, the direction ofcurrent flow between the cells disposed on the underside face (rearface) of the SOFC module is the same. The SOFC module is structured suchthat the respective cells are varied in area along the direction of thefuel flow. In FIGS. 6(a) to 6(c), there is shown one case where therespective cells sequentially increase in area along the direction ofthe fuel flow, as indicated by an arrow (→Z). Besides the above, as withthe case of Working Example 1 of the SOFC module structure, the SOFCmodule may be structured with respect to the respective rows asdescribed under items (1) to (3) given hereunder:

-   -   (1) One cell group is made up of a plurality of the cells        identical in area.

There are sequentially disposed the cell groups with the respectivecells thereof, sequentially increasing in area along the direction ofthe fuel flow.

-   -   (2) One cell group is made up of a plurality of cells identical        in area. There are sequentially, and alternately disposed the        cell groups, and the cells not belonging to any of the cell        groups (that is, individual cells) along the direction of the        fuel flow while the areas of the respective cells are        sequentially increased.    -   (3) One cell group is made up of a plurality of cells identical        in area. There are disposed the cell groups, and the cells not        belonging to any of the cell groups (that is, individual cells)        sequentially along the direction of the fuel flow, but at        random, while the areas of the respective cells are sequentially        increased along the direction of the fuel flow.

Further, the SOFC module is structured such that the cells disposed inthe respective rows, on a row-to-row basis, that is, on a sub-moduleunit basis, are varied in area along the direction of the fuel flow bythe row. FIGS. 7(a), 7(b), and FIGS. 8(a), 8(b) are views showingseveral examples of such modes, respectively. In those figures,respective rows from first to fourth rows indicate respective sub-SOFCmodules, omitting description of the interconnectors. In those examples,a plurality of the sub-modules are disposed such that faces thereof,with the cells disposed thereon, are in parallel with each other, and inthose figures, to show a mode of cell lineup, there are shown the facesthereof, on the side of the cell lineup. As shown in, for example, afigure on the right side in FIG. 9(a), FIGS. 10(a), 10(b), and so forth,referred to later on, fuel is in sequentially fed from the sub-module inthe forefront row to the sub-module in the row adjacent thereto, and soon. In FIGS. 7(a), 7(b), and 8(a), 8(b), reference numeral 19 denotes afuel flow path for respective SOFC sub-modules. Further, those figuresshow the case of the SOFC modules having four rows, however, the sameapplies to the case of the SOFC module having two to three rows, or fiveor more rows.

The example shown in FIG. 7(a) represents the case where the areas ofthe respective cells sequentially increase on the sub-module unit basis.In FIG. 7(a), the SOFC module is structured such that the areas of therespective cells 20 in the first row are small, the areas of therespective cells 20 in the second row, on the right side of the firstrow, are larger than those in the first row, the areas of the respectivecells 20 in the third row, on the right side of the second row, arelarger than those in the second row, and the areas of the respectivecells 20 in the fourth row, on the rightmost side, are larger than thosein the third row.

The example shown in FIG. 7(b) represents the case where the areas ofrespective cells are varied within a group of the cells, on a row-to-rowbasis, that is, within a sub-module unit, and further, the areas ofrespective cells are varied by the sub-module. In FIG. 7(b), the SOFCmodule is structured such that the respective areas of six cells 20 (agroup of six cells identical in area), on the lower end sides of boththe first row on the leftmost side, and the second row next to the firstrow, are smaller while the respective areas of five cells 20 (a group offive cells identical in area) above the six cells 20 are larger thanthose of the six cells 20. With respect to the third row on the rightside of the second row, four cells 20 (a group of four cells identicalin area) on the lower end side thereof are structured so as to besmaller in area while five cells 20 (a group of five cells identical inarea) above the four cells 20 are structured so as to be larger in areathan the four cells 20. With respect to the fourth row on the rightmostrow, five cells 20 (a group of five cells identical in area) on thelower end side thereof are structured so as to be smaller in area whilethree cells 20 (a group of three cells identical in area) above the fivecells 20 are structured so as to be larger in area than the five cells20.

With the example shown in FIG. 8(a), the respective cells 20 in each ofthe rows from the first row on the leftmost side to the third row arestructured so as to be identical in area while the respective cells 20in the fourth row are structured so as to be larger in area than thecells 20 in the respective rows from the first row to the third row.With the example shown in FIG. 8(b), the respective cells 20 in each ofthe rows from the first row on the leftmost side to the third row arestructured so as to identical in area, and with respect to therespective cells 20 in the fourth row on the rightmost side, six cells20 (a group of six cells identical in area) on the lower end sidethereof are structured so as to be smaller in area while five cells 20(a group of five cells identical in area) above the six cells 20 arestructured so as to be larger in area than the six cells 20.

In the cases of the examples of modes shown in FIGS. 7(a), 7(b), and8(a), 8(b), respectively, electric power is drawn out between the cellat the forefront of the first row, in the direction of the fuel flow,and the cell at the rearmost of the fourth row, in the direction of thefuel flow. The fuel is consumed at the respective cells to therebybecome gradually thinner along the direction of the fuel flow, however,since the respective cells or the respective cathodes thereof are variedin area along the direction of the fuel flow on a cell group unit basis,or a sub-module unit basis, the same effect as that in the case ofWorking Example 1 of the SOFC module structure, described hereinbefore,can be obtained. In addition, since the plurality of the cells areformed in each of the plurality of the rows from the first row to then-th row, so as to be electrically connected in series, a multitude ofthe cells can be lined up. Accordingly, large electric power can beobtained with a compact structure.

WORKING EXAMPLES OF A STRUCTURE OF SOLID OXIDE FUEL CELL COUPLED MODULES

There are described hereinafter Working Examples of a structure of solidoxide fuel cell bundled modules, according to the invention, that is,the structure for coupling up the solid oxide fuel cells made up asdescribed in the foregoing.

WORKING EXAMPLE 1 OF A STRUCTURE OF SOFC BUNDLED MODULES

FIGS. 9(a) to 9(c) are views showing Working Example 1 of a structurefor coupling up two units of the SOFC modules. In those figures,description of the cells and so forth, disposed on the respectivemodules is omitted. The same applies to Working Examples referred to inthe following figures up to FIG. 18. As show in FIG. 9(b), afemale-threaded hole 22 is provided in the lower part of the SOFC module21, on one-side face thereof, that is, on the fuel inlet side thereof,and the two units of the SOFC modules are disposed, opposite to eachother, with an interval provided therebetween, and in such a way as tobe plane parallel with each other. In FIG. 9(b), reference numeral 23denotes female-threads. An interval retaining hollow member 24 having ahollow protrusion provided with external threads so as to mate with thefemale-threaded holes 22 adjacent thereto is interposed between the twounits of the SOFC modules, which are securely held with each other byrotatively reciprocating the interval retaining hollow member 24. FIG.9(c) is a view showing the interval retaining hollow member 24, andreference numeral 25 denotes a hollow part thereof, that is, athrough-hole, reference numeral 26 denoting external-threads to be matedwith the female-threads 23. Since as the female-threads 23 of therespective female-threaded hole 22, use is made of female-threadscorresponding to the external-threads 26 provided on the hollowprotrusion of the interval retaining hollow member 24, both the modules21 can be coupled up and securely held with each other by simplyrotatively reciprocating the interval retaining hollow member 24.

The figure shown in the right side part of FIG. 9(a) shows the solidoxide fuel cell bundled modules structured as above, and the directionof fuel flow is indicated by an arrow (↑). In FIG. 9(a), referencenumeral 27 denotes a fuel guide pipe, and 28 an off-gas emission pipe. Apartition plate 29, as shown, for example, in the figure, is keptdisposed inside the respective modules 21 in such a way as to maintainspacing against the inner walls of the respective modules 21, at theupper end thereof. Reference numeral 30 denotes the spacing. Fuel fedinto the lower end of the module, on the left side in the figure, risesalong the partition plate 29, as indicated by the arrow (↑), is turnedback at the spacing 30 in the upper part of the module beforedescending, enters the module on the right side in the figure afterpassing through the through-hole 25 of the interval retaining hollowmember 24, rises again, is turned back at the spacing 30, at the upperend of the partition plate 29, before descending, and is subsequentlydischarged as spent fuel, that is, as an off-gas, from the lower end ofthe module on the right side. The partition plate 29 in the figure isshown by way of example, and it may be of any suitable construction ifit is capable of distributing the fuel by turning the same back in sucha way as described. In those respects, the same applies to WorkingExamples that will be described hereinafter. Further, in the figurescorresponding to respective Working Examples described hereinafter, thedirection of fuel flow is indicated by the arrow (↑) as appropriate.

WORKING EXAMPLE 2 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 2 represents a structure wherein 3 or more units of theSOFC modules are coupled up by the same technique as that for WorkingExample 1 described as above. FIGS. 10(a), and 10(b) are views showingWorking Example 2, in which FIG. 10(a) is a view showing the case ofcoupling up 3 units of the SOFC modules to be securely held with eachother, and FIG. 10(b) is a view showing the case of coupling up 4 ormore plural units of the SOFC modules to be securely held with eachother. In those figures, parts in common with those in FIGS. 9(a) to9(c), respectively, are denoted by like reference numerals. Of themodules disposed at both ends, respectively, the module 21 at theextreme left end of the SOFC bundled modules has a female-threaded holeprovided in the lower part (on the side of spent fuel emission) onone-side face thereof, and the module 21 at the extreme right end of theSOFC bundled modules has a female-threaded hole provided in the lowerpart (on the side of fuel feeding) on one-side face thereof while themodules 21 disposed between the modules at both the right and left ends,respectively, is provided with a female-threaded hole on respectivefaces thereof, on the side of the fuel feeding, and on the side of thespent fuel emission. As shown in FIGS. 10(a), and 10(b), the pluralunits of the modules are disposed in such a way as to be plane parallelwith each other with an interval provided between those adjacent to eachother to be thereby securely held together. An interval retaining hollowmember 24 for use in this case is the same in respect of construction,manner of securely holding the modules, and so forth as that for WorkingExample 1 described as above.

WORKING EXAMPLE 3 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 3 represents another structure for coupling up the SOFCmodules. FIGS. 11(a) to 11D, and FIGS. 12(a), 12(b) are views showingWorking Example 3. FIG. 11(a) is a view showing a state where 2 units ofthe modules 21 provided with an opening 36, respectively, are disposedside by side, an interval retaining hollow member 31 having a hollowprotrusion is interposed between the openings 36, and a screw bolt 30 isinserted in the openings 36. FIGS. 11(b) and 11(c) are views showing aconstruction of the interval retaining hollow member 31. The intervalretaining hollow member 31 has a protrusion 32, a skirting part 33provided on both sides thereof, and a through-hole 34 penetratingtherethrough. The through-hole 34 is larger in diameter than the shankof the screw bolt 30 to be inserted therein, and the skirting part 33 isstructured such that the outside diameter thereof is larger than thediameter of the through-hole 34.

Further, a figure on the left-hand side in FIG. 11(d) is a view showinga face of the module 21, on the head side of the screw bolt to beinserted, having a hole 35 corresponding to the diameter of the shank ofthe screw bolt. A figure on the right-hand side in FIG. 11(d) is a viewshowing a face of the module 21, on the side thereof, opposite to theface of the module 21, on the head side of the screw bolt, having anopening 36 corresponding to the diameter of the skirting part 33 of theinterval retaining hollow member 31.

As shown in FIG. 11(a), the 2 units of the modules 21 are disposed suchthat respective faces thereof, on the side provided with the opening 36,oppose each other, the interval retaining hollow member 31 is interposedtherebetween, and the shank of the screw bolt 30 is inserted into boththe hole 35 and the opening 36 of the module 21 on the left-hand side,and both the opening 36 and the hole 35 of the module 21 on theright-hand side. Thereafter, by tightening up a nut applied to theexternal threads of the screw bolt, the interval retaining hollow member31 is securely held between both the modules 21, in intimate contacttherewith. FIG. 12(a) shows the SOFC bundled modules made up in thisway. Use may be made of a screw bolt of a type to be tightened up withnuts from both sides of the screw bolt. FIG. 12(b) is a view showing aconfiguration between the interval retaining hollow member 31, and theshank, in such a case.

In the case of the present SOFC bundled modules, fuel is fed into thelower end of the module 21 on the left side in the figure, rises alongthe partition plate 29 as indicated by the arrow (↑), is turned back atthe upper end of the partition plate 29 before descending, enters themodule on the right side after passing through spacing 37 between theshank of the screw bolt, and the through-hole 34 of the intervalretaining hollow member 31, rises again, is turned back at the upper endof the partition plate 29, before descending, and is subsequentlydischarged as an off-gas, from the lower end of the module on the rightside, as shown in FIG. 12(a).

WORKING EXAMPLE 4 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 4 represents a structure wherein 3 or more units of theSOFC modules are coupled up by the same technique as that for WorkingExample 3 described as above. FIGS. 13(a), and 13(b) are views showingWorking Example 4, in which FIG. 13(a) is a view showing the case ofcoupling up 3 units of the SOFC modules to be securely held with eachother, and FIG. 13(b) is a view showing the case of coupling up 4 ormore plural units of the SOFC modules to be securely held with eachother. With the module 21 disposed between the modules 21 on both theright and left ends, respectively, a face thereof, on both side, areprovided with an opening 36 corresponding to the diameter of a skirtingpart 33 of an interval retaining hollow member 31, as shown in thefigure on the right-hand side in FIG. 11(d). The modules 21 on both theright and left ends, respectively, are the same in structure as thosefor Working Example 3.

As shown in FIGS. 13(a), and 13(b), the respective modules 21 aredisposed so to be in plane parallel with each other, the intervalretaining hollow member 31 is provided between those adjacent to eachother, respectively, and the shank of a screw bolt 30 is inserted fromone end thereof into the respective modules 21 as with the case ofWorking Example 3. Subsequently, in the case of the screw bolt 30provided with a head at one end thereof, the screw bolt 30 is tightenedup with a nut from the other end thereof, or in the case of the screwbolt 30 to be tightened up with a nut at both ends thereof, the screwbolt 30 is tightened up with the nut from both the ends thereof, therebycoupling up the respective modules 21 so as to be intimately andsecurely held with each other. In the case, the diameter of the screwbolt 30 is rendered smaller than the diameter of the opening 36, therebypermitting the fuel to be distributed between both parts. With the SOFCbundled modules made up in this way, fuel flow is the same as that inthe case of Working Example 3 described as above.

WORKING EXAMPLE 5 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 5 represents a structure wherein 2 or more units of theSOFC modules are coupled up without use of a screw bolt while WorkingExamples 3 and 4 of the structure of the SOFC bundled modules representthe case of securely holding the modules together by inserting the screwbolt into the interval retaining hollow member. FIG. 14, FIGS. 15(a),and 15(b) are views showing the present Working Example 5, showing thecase where 5 units of the modules are disposed in plane parallel witheach other to be thereby coupled up. FIG. 14 is a view showing theprocess of coupling up the modules, and FIGS. 15(a), and 15(b) are viewsshowing a configuration of the modules coupled up. FIG. 15(a) is alongitudinal sectional view, omitting description of a heat insulatingmaterial located at the top and bottom of each of the modules, a fuelguide pipe, and so forth. FIG. 15(b) is a sectional view taken on lineA-A in FIG. 15(a).

As shown in FIG. 14, among the 5 units of the modules 21, the modules atboth the right and left ends, respectively, each have an opening 38provided on one side (on the side of fuel feeding) of one-side facethereof, in the longitudinal direction, and 3 units of the modules,other than those at both the right and left ends, each have an opening39 provided on one side (on the side of fuel feeding) of each of theboth faces thereof, in the longitudinal direction. The respectivediameters of the openings 38, 39 are equal to the outside diameter ofthe same skirting part 33 of the interval retaining hollow member 31 asis shown FIG. 11(c).

As shown in FIG. 14, the interval retaining hollow member 31 isinterposed to be securely held between the openings 38, 39, opposite toeach other, between the openings 39, 39, opposite to each other, andbetween the openings 39, 38, opposite to each other, respectively, amongthose openings. As means for securely holding the interval retaininghollow member 31, use may be made of a sintering process. In this case,the respective openings, and the skirting parts 33 of the respectiveinterval retaining hollow members 31 are intimately and securely heldwith each other by sintering. The sintering process can be applied toWorking Examples 6 to 8 that will be described hereinafter. Further, inimplementing such secure holding as described, the modules in whole maybe disposed inside a casing 40 to be thereby securely held with eachother, as shown in FIGS. 15(a), and 15(b). In this case, the secureholding may be carried out by use of the sintering process incombination with the above-described method. Further, upon disposing themodules in whole inside the casing 40, an elastic member 41, such asspring, and so forth, may be disposed between either or both of themodules at both the right and left ends, and the inner wall of thecasing 40, thereby intimately and securely holding those parts with eachother. FIGS. 15(a), and 15(b) show the case of disposing the elasticmember 41, such as spring, and so forth, between either of therespective modules at both the right and left ends, and the inner wallof the casing 40. In FIG. 15(a), the direction of fuel distribution isindicated by an arrow (↑). FIG. 14, FIGS. 15(a), and 15(b), there isshown the case where the 5 units of the modules are coupled up, andsecurely held with each other, however, the same applies to the casewhere 2 to 4 units, or 6 or more units of the modules are coupled up,and securely held with each other.

WORKING EXAMPLE 6 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 6 represents a structure wherein the SOFC modules arecoupled up on the side of spent fuel emission as well as fuel feedingwhile Working Examples 1 to 5 of the structure of the SOFC bundledmodules, respectively, represent the case of coupling up the SOFCmodules on the side of fuel feeding. FIGS. 16(a) and 16(b) are viewsshowing the present Working Example 6. With Working Example 6, only thesame interval retaining hollow member 31 as is shown in FIG. 11(c) isused as a coupling member. Further, with Working Example 6, there is noneed for installing the partition plate 29 for guiding fuel flow,required in Working Examples 1, and so forth, or a member equivalentthereto, inside the respective modules.

The respective modules are provided with an opening on the side of spentfuel emission as well as fuel feeding. The respective diameters of thoseopenings are equal to the outside diameter of a skirting part 33 of theinterval retaining hollow member 31. In this case, however, as shown inFIGS. 16(a) and 16(b), the module at the leftmost end is provided withthe opening on the side of spent fuel emission only, and the module atthe rightmost end is provided with the opening on the side of fuelfeeding only. Then, as shown in FIGS. 16(a) and 16(b), the intervalretaining hollow member 31 is interposed between the respective openingsof the modules neighboring on each other, that is, the adjacent modules,opposite to each other, respectively, and the modules in whole aredisposed inside a casing 40. In FIG. 16(b), there is shown the casing 40in as-partially cut-away state. With the bundled modules made up bydisposing a plurality of the modules as described above, fuel is fedinto the module at the leftmost end from a fuel guide pipe 42 in thelower part thereof to be distributed as indicated by an arrow (↑) inFIG. 16(a) so as to contribute to power generation, and is sequentiallydistributed to the respective modules neighboring on each other to bethereby discharged as spent fuel, that is, an off-gas from an off-gasemission pipe 43 in the upper part of the module at the rightmost end.

WORKING EXAMPLE 7 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 7 is the same as Working Example 6 in that the SOFCmodules are coupled up on the side of spent fuel emission as well asfuel feeding, but represents a structure wherein coupling between therespective modules is implemented with an interval retaining unhollowmember as well as an interval retaining hollow member. FIGS. 17(a) to17(c) are views showing Working Example 7. In FIG. 17(a), description ofa casing 40 is omitted, and FIG. 17(b) is a plan view of Working Example7 shown in FIG. 17(a) as seen from above. In FIG. 17(b), there is shownthe casing 40 in as-partially cut-away state. In this case, as theinterval retaining hollow member, use is made of the same intervalretaining hollow member 31 as is shown in FIG. 11(c) while as theinterval retaining unhollow member, use is made of an interval retainingmember 44 as shown in FIG. 17(c). As shown in FIG. 17(c), the intervalretaining member 44 that is not hollow is the same in construction asthe interval retaining hollow member 31 except that the former does nothave the through-hole 34 provided in the interval retaining hollowmember 31, that is, a fuel flow path.

As shown in FIG. 17(a), the interval retaining hollow member 31, and theinterval retaining member 44 that is not hollow are disposed in theupper part and lower part of the respective modules, in a staggeredfashion. The interval retaining member 44 that is not hollow functionsas an interval retaining member, thereby attaining improvement onretention of an interval between the respective modules adjacent to eachother, and secure holding therebetween. Otherwise, Working Example 7 issimilar to the case of Working Example 6.

WORKING EXAMPLE 8 OF A STRUCTURE OF SOFC BUNDLED MODULES

Working Example 8 has the same structure for coupling up a plurality ofthe SOFC modules as that for Working Examples 5, and so forth, however,the present Working Example 8 is structured such that pressure lossoccurs at parts of the respective modules, where fuel inside therespective modules is released to outside. With Working Example 8, thereis no need for installing a partition plate 29 for guiding fuel flow, ora member equivalent thereto, inside the respective modules because thefuel fed into the respective modules is released from the respectivemodules, individually, to outside.

FIG. 18 is a view showing the present Working Example 8. As shown inFIG. 18, a fuel guide pipe 42 is provided only in the module at theforefront, and a spent fuel emission pipe 43 is provided in therespective modules. Further, the spent fuel emission pipes 43 of therespective modules are sequentially increased in inside diameter fromthe leftmost module toward the rightmost module. The fuel fed into themodule at the forefront branches off into the next module through a holeof an interval retaining hollow member 31, and thereafter, issequentially fed to the respective modules in the similar manner. WithWorking Example 8, pressure loss occurs to the module with the spentfuel emission pipe 43 large in inside diameter when the cells areoperated, whereupon a portion of the fuel fed into the moduleimmediately preceding to the relevant module, corresponding to thepressure loss, is fed into the module subsequent to the relevant modulethrough the interval retaining hollow member 31. FIG. 18 shows the casewhere 5 units of the modules are coupled up and securely held together,however, the same applies to the case where 2 to 4 units, or 6 or moreunits of the modules are coupled up and securely held together,

FIG. 19 shows a type for feeding fuel in a room temperature region,structured such that fuel flow to the respective modules is adjusted byroom temperature so as to be rendered equal. As shown in FIG. 19, fuelis caused to branch off from a common fuel feed pipe 45 to be fed intothe respective modules via respective fuel guide pipes 46. For acoupling member (not shown) between the respective modules, use may bemade of either the interval retaining member 44 that is not hollow asshown in FIG. 17(c), or the interval retaining hollow member 31 as shownin FIG. 11(c). In the case of using the interval retaining hollow member31, fuel is distributed mutually between the respective modules adjacentto each other through a hollow part, that is, the through-hole 34.

Construction for Configuration of Current Drawing Conductors

With the respective SOFC modules structured as described in theforegoing, and the respective SOFC bundled modules (that is, the SOFCmodules made up by coupling up the plurality of the SOFC modules),electric power is drawn out via a conductor leading from the anode atthe forefront in the direction of fuel flow, and via a conductor leadingfrom the cathode at the rearmost in the direction of the fuel flow. Withthe present invention, both the conductors are disposed on the anodeside of the respective SOFC modules, and all current is drawn out from afuel flow path side thereof, thereby enabling degradation of both theconductors to be prevented. That is, since SOFC fuel is a reducing gassuch as hydrogen, carbon monoxide, or methane, the conductors are notoxidized. FIG. 20 is a view showing an example of a construction forconfiguration of the conductors for drawing out current. There isprovided an electrolyte between an anode 48, and a cathode 49, however,description of the electrolyte is omitted in FIG. 20. In FIG. 20,reference numeral 50 denotes an interconnector. Further, in FIG. 20,there is shown the case of using the same interval retaining hollowmember 31 as is shown in FIG. 11(c) for an interval retaining member 55,however, the same applies to the case of using other interval retainingmembers such as one shown in FIG. 17(c).

As shown in FIG. 20, a current-drawing conductor 51 from the anode 48 iscaused to lead to a conductor 53 provided on the inner side of aninsulator substrate 47, and a current-drawing conductor 52 from thecathode 49 is caused to lead to a conductor 54 provided on the innerside of the insulator substrate 47. That is, both the conductors 53, 54are caused to lead to the inside of the internal fuel flow part. In thiscase, since current drawn from the anode 48, and the cathode 49,respectively, is guided to the conductors 53, 54 disposed at the innerside of the insulator substrate 47, respectively, through theintermediary of the interval retaining member 55, the interval retainingmember 55 also needs to be electroconductive. Accordingly, the intervalretaining member 55 itself is made of an electroconductive material,however, the interval retaining member 55 can be renderedelectroconductive by an appropriate method other than that, such as (1)a method of plating the surface of the interval retaining member 55 withan electroconductive metal such as Ag, Pt, and so forth, (2) a method ofcausing the interval retaining member 55 to contain theelectroconductive metal such as Ag, Pt, and so forth, (3) a method ofdisposing conductors leading to the conductor 51 from the anode 48, andthe conductor 52 from the cathode 49, respectively, inside the insulatorsubstrate 47, thereby causing the conductors to be electricallycontinuous with the conductors 53, 54, respectively.

It is quite useful to render the interval retaining member 55electroconductive as described above because electrical connectionbetween the adjacent modules can be implemented by so doing. Referringto FIG. 20, in the figure, the interconnector designated as “a”, and theinterconnector designated as “b” need to be electrically continuous,however, by rendering the interval retaining member 55 electroconductiveas described above, electrical connection between the interconnector“a”, and the interconnector “b” can be implemented.

Construction for Configuration of Interconnector between Adjacent Cells

With the respective SOFC modules structured as described in theforegoing, and the respective SOFC bundled modules, the interconnectoris disposed between the adjacent cells. With the present invention, if adense material, as the constituent material of the interconnector, isused between respective electrolytic films of the adjacent cells, acoarse material can be used between the cathode and the dense material.The interconnector is a conductor linking between the adjacent cells,that is, linking the cathode of the preceding cell, with the anode ofthe immediately following cell, and can be structured in the shape of asheet, wire, or in other appropriate shapes.

Herein, in the description of the present invention, the term “dense” inthe dense material described as above means having density correspondingto not less than 90%, preferably not less than 95% of the theoreticaldensity of the material. In contrast, in the description of the presentinvention, the term “coarse” in the coarse material described as abovemeans having density in a range of from 20% to less than 90% against thetheoretical density of the material. With the present invention, for theconstituent material of the interconnector, use is made of both thedense material, and the coarse material, however, it is essential to useat least the dense material between the respective electrolytic films ofthe adjacent cells, and on that premise, the dense material may be usedin place of the coarse material at spots where the coarse materialdescribed hereinafter is to be used.

If the constituent material of the interconnector is, for example, (La,Sr) CrO₃, this material has poor sinterability, so that it is extremelydifficult to implement fabrication of the interconnector out of thesame. Accordingly, with the present invention, at least the densematerial is used as material for the interconnector between the adjacentcells. As a result, gas-sealing performance is enhanced, therebypreventing gas from leaking between the interconnector and theelectrolyte. In addition, with the use of the dense material, electricalcontact can be secured. Further, as described above, the coarse materialcan be used between the cathode and the dense material. By so doing, itis possible to obtain an advantageous effect that the fabrication of theinterconnector can be implemented concurrently with the formation of thecathode, or at a temperature lower than the sintering temperature of thecathode.

Configuration Construction 1 of Interconnectors

FIG. 21 is a view showing configuration construction 1 ofinterconnectors. A figure shown in the lower part of FIG. 21 is apartially enlarged view of a figure shown in the upper part of FIG. 21.In this respect, the same applies to FIGS. 22 to 31 referred tohereinafter. In FIG. 21, reference numeral 56 denotes a porous insulatorsubstrate, 57 an anode, 58 an electrolyte, and 59 a cathode, and in thisrespect, the same applies to FIGS. 22 to 31 referred to hereinafter.Further, the underside face of the interconnector [in FIG. 21, a portionindicated as “interconnector (need not be dense)”] is normally incontact with the upper face of the electrolyte 58, however, there can bethe case where spacing exists therebetween. FIG. 21 shows the case wherethe spacing, as indicated by S in the figure, exists therebetween, butthe spacing may be filled up with an interconnector material, and soforth. In this respect, the same applies to FIGS. 22 to 26, and FIGS. 28to 31, referred to hereinafter.

A dense portion of the interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 21). With the presentconfiguration construction 1, the dense material is used between theadjacent electrolytes 58, while the coarse material is used between thecathode 59 and the dense material. In the case of material composedmainly of an oxide expressed by, for example, chemical formula (Ln, A)CrO₃ (in the chemical formula, Ln refers to lanthanoids, and A refers toBa, Ca, Mg, or Sr), this material has poor sinterability, so that it isextremely difficult to implement fabrication of the interconnector outof the same. Accordingly, as with the present configuration construction1, by use of the dense material between the adjacent electrolytes 58,gas-sealing performance can be enhanced, and gas can be prevented fromleaking between the interconnector and the electrolytes. In addition,with the use of the dense material, electrical contact can be secured.

In general, the interconnector is linked with the anode 57 by disposingthe interconnector underneath the anode 57. In contrast, by causing thedense material for the interconnector to be present on the upper face ofthe anode 57, as shown in FIG. 21, the fabrication can be facilitated.Further, as there is adopted the construction wherein parts of theelectrolyte 58 are covered by the interconnector, sealing performancecan be enhanced. In respect of the use of the coarse material betweenthe cathode 59 and the dense material, the same applies to configurationconstructions that will be described hereinafter.

Configuration Construction 2 of Interconnectors

FIG. 22 is a view showing configuration construction 2 ofinterconnectors. A dense portion of an interconnector is disposedbetween the adjacent cells (the cells disposed side by side in FIG. 22).With the configuration construction 2, the dense material is disposed ona part of the top face of the anode 57 between the adjacent electrolytes58, and a portion of the dense material is linked with the coarsematerial. By so doing, there is made up a construction wherein the topof the dense material except a coarse material portion of theinterconnector is covered by the electrolytes 58. In other respects, thestructure of the present configuration construction 2 is the same asthat for the configuration construction 1. The present configurationconstruction 2 being of the construction wherein the top of the densematerial is covered by the electrolytes 58, gas-sealing performance canbe further enhanced.

Configuration Construction 3 of Interconnectors

FIG. 23 is a view showing configuration construction 3 ofinterconnectors. An interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 23). With theconfiguration construction 3, the dense material is disposed between theadjacent electrolytes 58, and on the top face of the anode 57, and aside face thereof, continuous to the top face. By so doing, a contactarea between the dense material for the interconnector, and theelectrolytes 58 can be increased, thereby enabling contact resistancebetween the interconnector and the anode 57 to be lowered. In otherrespects, the structure of the present configuration construction 3 isthe same as that for the configuration construction 2.

Configuration Construction 4 of Interconnectors

FIG. 24 is a view showing configuration construction 4 ofinterconnectors. A dense portion of an interconnector is disposedbetween the adjacent cells (the cells disposed side by side in FIG. 24).With the present configuration construction 4, the dense material forthe interconnector is disposed between the adjacent electrolytes 58, andon a side face of the anode 57, continuous to the former. As shown inFIG. 24, the dense material is in a sectional shape resembling theletter T, and the underside face of the head thereof is in contact withthe electrolytes 58 while most (that is, except a portion thereof,penetrated by the electrolyte 58) of one side face of the leg thereof isin contact with the anode 57, and the other side face of the leg thereofis in contact with the electrolyte 58. By so doing, a contact areabetween the dense material for the interconnector, and the electrolytes58 can be increased, and contact resistance between the interconnector,and the anode 57 can be lowered, thereby enabling sealing performance tobe enhanced. In other respects, the structure of the presentconfiguration construction 4 is the same as that for the configurationconstruction 1.

Configuration Construction 5 of Interconnectors

FIG. 25 is a view showing configuration construction 5 ofinterconnectors. A dense portion of an interconnector is disposedbetween the adjacent cells (the cells disposed side by side in FIG. 25).With the present configuration construction 5, the dense material forthe interconnector is structured so as to continue from the top face ofthe electrolyte 58 of the preceding cell of the adjacent cells to a sideface of the electrolyte 58, coming into contact with the top face of theporous insulator substrate 56, and to subsequently come into contactwith a side face of the anode 57 of the immediately following cellbefore further continuing to the top face thereof. As a result, theelectrolytes 58 can be completely separated from each other incomparison with the case of the interconnector configurationconstruction 4. That is, the respective electrolytes 58 of the adjacentcells are separated from each other. With the present configurationconstruction 5, gas leakage from the porous insulator substrate 56 canbe sealed with the dense material for the interconnector.

Configuration Construction 6 of Interconnectors

FIG. 26 is a view showing configuration construction 6 ofinterconnectors. An interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 26). With the presentconfiguration construction 6, the dense material for the interconnectoris structured so as to continue from the top face of the electrolyte 58of the preceding cell of the adjacent cells to a side face thereof,coming in contact with the top face of the porous insulator substrate56, and to come into contact with a side face of the anode 57 of theimmediately following cell before continuing to the underside face ofthe electrolyte 58. As a result, the respective electrolytes 58 of theadjacent cells are separated from each other as with the case of theconfiguration construction 5. In addition, the cathode 59 is disposed onthe top face of the electrolyte 58. With the present configurationconstruction 6, sealing performance against gas leakage from the porousinsulator substrate 56 can be enhanced with the dense material for theinterconnector.

Configuration Construction 7 of Interconnectors

FIG. 27 is a view showing configuration construction 7 ofinterconnectors. An interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 27). With the presentconfiguration construction 7, the electrolytes 58 of the respectivecells are disposed so as to cover the anode 57 including a side facethereof. With the present configuration construction 7, the densematerial for the interconnector is structured so as to continue from thecathode 59 of the preceding cell of the adjacent cells to the top faceof the electrolyte 58, coming in contact with a side face thereof, andto subsequently come into contact with the top face of the porousinsulator substrate 56, further continuing to the underside face of theelectrolyte 58 of the immediately following cell. As a result, therespective electrolytes 58 of the adjacent cells are separated from eachother. With the present configuration construction 7, sealingperformance against gas leakage from the porous insulator substrate 56can be enhanced with the dense material for the interconnector. In thecase where the dense material for the interconnector is composed of, forexample, an Ag-containing material, there can be at times when Ag isscattered if Ag is in single substance form. Accordingly, with thepresent configuration construction 7, the top of the Ag-containingmaterial is covered with a glass material, and so forth, as shown inFIG. 27, thereby preventing scattering of Ag.

Configuration Construction 8 of Interconnectors

FIG. 28 is a view showing configuration construction 8 ofinterconnectors. An interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 28). As shown in asectional view of FIG. 28, the respective cells are structured such thata side face of the both side faces of the anode 57, on the upstream sideof fuel flow, is not covered with the electrolyte 58 while the otherside face of the anode 57, on the downstream side of the fuel flow, iscovered with the electrolyte 58, and the electrolyte 58 covers the topface of the insulator substrate 56. Further, a dense portion of theinterconnector is structured so as to continue from the electrolyte 58on the top face of the insulator substrate 56 (between the electrolyte58 and the top face of the insulator substrate 56), coming in contactwith the top face of the insulator substrate 56 to a side face of theanode 57 of the immediately following cell before coming into contactwith the top face of the electrolyte 58. As a result, the respectiveelectrolytes 58 of the adjacent cells are separated from each other.With the present configuration construction 8, the electrolytes 58 arecompletely separated from each other, that is, the respectiveelectrolytes 58 of the adjacent cells are separated from each other, andby disposing the dense portion of the interconnector on the top face ofthe electrolyte 58, on the side of the cell, adjacent to the anode 57with which the dense portion of the interconnector comes into contact,sealing performance can be enhanced. Further, since the electrolyte 58covers between the side face of the anode 57, on the downstream side ofthe fuel flow, and the top face of the insulator substrate 56, sealingperformance can be enhanced.

Configuration Construction 9 of Interconnectors

FIG. 29 is a view showing configuration construction 9 ofinterconnectors. An interconnector is disposed between the adjacentcells (the cells disposed side by side in FIG. 29). As shown in asectional view of FIG. 29, the respective cells are structured such thata side face of the both side faces of the anode 57, on the upstream sideof fuel flow, is not covered with the electrolyte 58 while the otherside face of the anode 57, on the downstream side of the fuel flow, iscovered with the electrolyte 58, and the electrolyte 58 covers the topface of part of the insulator substrate 56. Further, a dense portion ofthe interconnector is structured so as to continue from the electrolyte58 on the top face of the part of the insulator substrate 56, cominginto contact with the top face of the insulator substrate 56, to a sideface of the anode 57 of the immediately following cell before cominginto contact with the underside face of the electrolyte 58 (that is,between the underside face of the electrolyte 58 and the anode 57). As aresult, the respective electrolytes 58 of the adjacent cells areseparated from each other. With the present configuration construction9, the electrolytes 58 are completely separated between the respectivecells, that is, the respective electrolytes 58 of the adjacent cells arecompletely separated from each other. Thus, by disposing the denseportion of the interconnector so as to continue from the electrolyte 58on the top face of the part of the insulator substrate 56, coming intocontact with the top face of the insulator substrate 56, to the sideface of the anode 57 of the immediately following cell before cominginto contact with the underside face of the electrolyte 58 (that is,between the underside face of the electrolyte 58 and the anode 57), asdescribed above, sealing performance can be enhanced.

Configuration Construction 10 of Interconnectors

FIG. 30 is a view showing configuration construction 10 ofinterconnectors. A dense portion of an interconnector is disposedbetween the adjacent cells (the cells disposed side by side in FIG. 30).As shown in a sectional view of FIG. 30, with the interconnectorconfiguration construction 10, the respective cells are structured suchthat a side face of the both side faces of the anode 57, on the upstreamside of fuel flow, is not covered with the electrolyte 58 while theother side face of the anode 57, on the downstream side of the fuelflow, is covered with the electrolyte 58, and the electrolyte 58 coversthe top face of part of the insulator substrate 56. Further, the denseportion of the interconnector is structured so as to continue from thetop face of the electrolyte 58 on the top face of the part of theinsulator substrate 56, coming into contact with the top face of theinsulator substrate 56, to a side face of the anode 57 of theimmediately following cell before coming into contact with the undersideface of the electrolyte 58 (that is, between the underside face of theelectrolyte 58 and the anode 57). With the interconnector configurationconstruction 10, the electrolytes 58 are completely separated betweenthe respective cells, that is, the respective electrolytes 58 of theadjacent cells are completely separated from each other. Thus, bydisposing the dense portion of the interconnector so as to continue fromthe top face of the electrolyte 58 on the top face of the part of theinsulator substrate 56, coming into contact with the top face of theinsulator substrate 56, to the side face of the anode 57 of theimmediately following cell before coming into contact with the undersideface of the electrolyte 58 (that is, between the underside face of theelectrolyte 58 and the anode 57), as described above, sealingperformance can be enhanced.

Configuration Construction 11 of Interconnectors

FIG. 31 is a view showing interconnector configuration construction 11of interconnectors. As shown in a sectional view of FIG. 31, with thepresent interconnector configuration construction 11, the respectivecells are structured such that a side face of the both side faces of theanode 57, on the upstream side of fuel flow, is not covered with theelectrolyte 58 while the other side face of the anode 57, on thedownstream side of the fuel flow, is covered with the electrolyte 58,and the electrolyte 58 covers the top face of part of the insulatorsubstrate 56. Further, the dense portion of the interconnector isstructured so as to continue from the top face of the electrolyte 58 onthe top face of the part of the insulator substrate 56, coming intocontact with the top face of the insulator substrate 56, to a side faceof the anode 57 of the immediately following cell before coming intocontact with the top face of the electrolyte 58. With the presentconfiguration construction 11, the electrolytes 58 are completelyseparated between the respective cells, that is, the respectiveelectrolytes 58 of the adjacent cells are completely separated from eachother. Thus, by disposing the dense portion of the interconnector so asto continue from the top face of the electrolyte 58 on the top face ofthe part of the insulator substrate 56, coming into contact with the topface of the insulator substrate 56, to the side face of the anode 57 ofthe immediately following cell before coming into contact with the topface of the electrolyte 58, as described above, sealing performance canbe enhanced.

1. A solid oxide fuel cell module comprising: a substrate with aninternal fuel flow part provided therein, at least a face thereof, incontact with cells, and interconnectors, being an insulator; a pluralityof the cells each comprised of an anode, an electrolyte, and a cathode,stacked in sequence, formed on a surface of the substrate; and theinterconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow.
 2. A solid oxide fuel cell modulecomprising: a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed in each of a plurality of rows from first to n-th rowson a surface of the substrate; and the interconnectors each electricallyconnecting in series the cells adjacent to each other, wherein therespective cells are varied in area along the direction of fuel flow. 3.A solid oxide fuel cell module according to claim 1, wherein a structurein which the respective cells are varied in area along the direction offuel flow is a structure in which the respective cells sequentiallyincreases in area along the direction of the fuel flow.
 4. A solid oxidefuel cell module according to claim 1, wherein the structure in whichthe respective cells are varied in area along the direction of fuel flowis a structure in which a cell group is made up of a plurality of thecells identical in area, and a plurality of the cell groups with therespective cells thereof, sequentially increasing in area along thedirection of the fuel flow by the cell group, are sequentially disposed.5. A solid oxide fuel cell module according to claim 1, wherein thestructure in which the respective cells are varied in area along thedirection of fuel flow is a structure in which a cell group is made upof a plurality of the cells identical in area, and the cell groups, andthe cells not belonging to any of the cell groups are disposedalternately or at random such that the areas of the respective cells aresequentially increased along the direction of the fuel flow.
 6. A solidoxide fuel cell module according to claim 1, wherein the substrate withthe internal fuel flow part provided therein, at least the face thereof,in contact with the cells, and the interconnectors, being the insulator,is a substrate polygonal, elliptical, or tubular in cross-sectionalshape.
 7. A solid oxide fuel cell module according to claim 1, whereinthe substrate with the internal fuel flow part provided therein, atleast the face thereof, in contact with the cells, and theinterconnectors, being the insulator, is a substrate with Ni diffusedtherein.
 8. A solid oxide fuel cell module according to claim 7, whereinan amount of the Ni diffused corresponds to not more than 35 vol. %. 9.A solid oxide fuel cell module according to claim 1, wherein theconstituent material of the substrate with the internal fuel flow partprovided therein, at least the face thereof, in contact with the cells,and the interconnectors, being the insulator, is material composed of amixture of MgO, and MgAl₂O₄, a zirconia based oxide, or a mixture of thezirconia based oxide, MgO, and MgAl₂O₄.
 10. A solid oxide fuel cellmodule according to claim 9, wherein the mixture of MgO, and MgAl₂O₄ isa mixture of MgO and MgAl₂O₄, containing 20 to 70 vol. % of MgO.
 11. Asolid oxide fuel cell module according to claim 1, wherein theconstituent material of the interconnector connecting the anode to thecathode between the respective cells adjacent to each other is materialcomposed mainly of an oxide expressed by chemical formula (Ln, A) CrO₃(in chemical formula, Ln refers to lanthanoids, and A refers to Ba, Ca,Mg, or Sr).
 12. A solid oxide fuel cell module according to claim 1,wherein the constituent material of the interconnector connecting theanode to the cathode between the respective cells adjacent to each otheris an oxide material containing Ti.
 13. A solid oxide fuel cell moduleaccording to claim 12, wherein the oxide material containing Ti is MTiO₃(in chemical formula, M refers to at least one element selected from thegroup consisting of Ba, Ca, Pb, Bi, Cu, Sr, La, Li, and Ce).
 14. A solidoxide fuel cell module according to claim 1, wherein the constituentmaterial of the interconnector connecting the anode to the cathodebetween the respective cells adjacent to each other is material composedmainly of Ag.
 15. A solid oxide fuel cell module according to claim 14,wherein the material composed mainly of Ag is material composed of onesubstance or not less than two substances, selected from the groupconsisting of Ag, Ag solder, and a mixture of Ag and glass.
 16. A solidoxide fuel cell module according to claim 1, wherein the constituentmaterial of the interconnector connecting the anode to the cathodebetween the respective cells adjacent to each other is material composedmainly of Ag, and the interconnector is covered with glass.
 17. A solidoxide fuel cell module according to claim 1, wherein the constituentmaterial of the interconnector connecting the anode to the cathodebetween the respective cells adjacent to each other is material composedof two kinds of materials, that is, a material expressed by chemicalformula (La_(1-x)Sr_(x)) CrO₃ (in chemical formula, x=0 to 0.6)deposited on a metal.
 18. A solid oxide fuel cell module according toclaim 1, wherein the constituent material of the interconnectorconnecting the anode to the cathode between the respective cellsadjacent to each other is material composed of two kinds of materials,that is, a material expressed by chemical formula (La_(1-x)Sr_(x)) CrO₃(in chemical formula, x=0 to 0.6) deposited on a material composedmainly of Ag.
 19. A solid oxide fuel cell module according to claim 1,further comprising an interface layer between the electrolyte and thecathode.
 20. Solid oxide fuel cell bundled modules comprising: two unitsof solid oxide fuel cell modules disposed with an interval providedtherebetween, and in such a way as to be plane parallel with each other,said solid oxide fuel cell module comprising; a substrate with aninternal fuel flow part provided therein, at least a face thereof, incontact with cells, and interconnectors, being an insulator; a pluralityof the cells each comprised of an anode, an electrolyte, and a cathode,stacked in sequence, formed on a surface of the substrate; and theinterconnectors each electrically connecting in series the cellsadjacent to each other, wherein the respective cells are varied in areaalong the direction of fuel flow, the respective modules being providedwith a female-threaded hole, on one-side faces thereof, opposing eachother, on the fuel inlet side thereof, and an interval retaining hollowmember having a skirting part provided with external threads so as tomate with the respective female-threaded holes adjacent thereto beinginterposed between the female-threaded holes, wherein said two units ofthe solid oxide fuel cell modules are securely held with each other byrotatively reciprocating the interval retaining hollow member.
 21. Solidoxide fuel cell bundled modules comprising: plural units of solid oxidefuel cell modules disposed in such a way as to be plane parallel witheach other to be coupled together, said solid oxide fuel cell modulecomprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, two modules at both extreme ends, respectively, among saidplural units of the solid oxide fuel cell modules, being provided with afemale-threaded hole, on one-side faces thereof, on the fuel inlet sidethereof, while the respective modules between the two modules at boththe extreme ends, respectively, being provided a female-threaded hole,on both-side faces thereof, on the fuel inlet side thereof, and aninterval retaining hollow member having a skirting part provided withexternal threads so as to mate with the respective female-threaded holesadjacent thereto being interposed between the female-threaded holesadjacent to each other, wherein the respective solid oxide fuel cellmodules are securely held with each other by rotatively reciprocatingthe respective interval retaining hollow members.
 22. Solid oxide fuelcell bundled modules comprising: two units of solid oxide fuel cellmodules disposed with an interval provided therebetween, and in such away as to be plane parallel with each other, said solid oxide fuel cellmodule comprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, the respective modules being provided with an opening, onone-side faces thereof, opposite to each other, on the fuel inlet sidethereof, and also a hole corresponding to the diameter of the shank of ascrew bolt on the other side faces thereof, opposite from the openingsof the respective modules, while an interval retaining hollow memberhaving a skirting part corresponding to the respective openings beinginterposed between the openings, wherein said two units of the solidoxide fuel cell modules are securely held with each other by insertingthe screw bolt with a head at one end thereof, or the screw bolt withthreads at both ends thereof into the holes, openings, and a hollow partof the interval retaining hollow member, from one end of the screw bolt,and tightening up with a nut, or nuts.
 23. Solid oxide fuel cell bundledmodules comprising: plural units of solid oxide fuel cell modulesdisposed with an interval provided therebetween, and in such a way as tobe plane parallel with each other, said solid oxide fuel cell modulecomprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, two modules at both the extreme ends, respectively, amongsaid plural units of the solid oxide fuel cell modules, being providedwith an opening, on one-side faces thereof, on the fuel inlet sidethereof, and also a hole corresponding to the diameter of the shank of ascrew bolt on the other side faces thereof, opposite from the respectiveopenings of the two modules at both the extreme ends, respectively,while the respective modules between the two modules at both the extremeends, respectively, being provided an opening, on both-side facesthereof, on the fuel inlet side thereof, and an interval retaininghollow member having a skirting part provided with external threads soas to mate with the respective openings adjacent thereto beinginterposed between the adjacent openings, wherein the respective solidoxide fuel cell modules are securely held with each other by insertingthe screw bolt with a head at one end thereof, or the screw bolt withthreads at both ends thereof into the holes, openings, and a hollow partof the interval retaining hollow member, from one end of the screw bolt,and tightening up with a nut, or nuts.
 24. Solid oxide fuel cell bundledmodules comprising: plural units of solid oxide fuel cell modulesdisposed with an interval provided therebetween, and in such a way as tobe plane parallel with each other, said solid oxide fuel cell modulecomprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, two modules at both the extreme ends, respectively, amongsaid plural units of the solid oxide fuel cell modules, being providedwith an opening, on one-side faces thereof, on the fuel inlet sidethereof while the respective modules between the two modules at both theextreme ends, respectively, being provided an opening, on both-sidefaces thereof, on the fuel inlet side thereof, and an interval retaininghollow member having a skirting part matching the respective openingsadjacent thereto being interposed between the adjacent openings, whereinthe solid oxide fuel cell modules in whole are disposed inside a casingto be securely held with each other.
 25. Solid oxide fuel cell bundledmodules comprising: plural units of solid oxide fuel cell modulesdisposed with an interval provided therebetween, and in such a way as tobe plane parallel with each other, said solid oxide fuel cell modulecomprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, the module of said plural units of the solid oxide fuel cellmodules, at the forefront in the direction of the fuel flow, beingprovided with an opening on the fuel feeding side thereof while therespective modules subsequent to the module at the forefront beingprovided openings on the spent fuel emission and fuel feeding sidesthereof, respectively, and an interval retaining hollow member having askirting part being interposed between the openings of the respectivemodules adjacent to each other, opposite to each other, wherein thesolid oxide fuel cell modules in whole are disposed inside a casing tobe securely held with each other,
 26. Solid oxide fuel cell bundledmodules comprising: plural units of solid oxide fuel cell modulesdisposed with an interval provided therebetween, and in such a way as tobe plane parallel with each other, said solid oxide fuel cell modulecomprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, the module of said plural units of the solid oxide fuel cellmodules, at the forefront in the direction of the fuel flow, beingprovided with an opening on the fuel feeding side thereof while therespective modules subsequent to the module at the forefront beingprovided openings on the spent fuel emission and fuel feeding sidesthereof, respectively, and an interval retaining hollow member having askirting part, and an interval retaining unhollow member having askirting part being interposed between the openings of the respectivemodules adjacent to each other, opposite to each other, in the upperpart and lower part of the respective modules, in a staggered fashion,wherein the solid oxide fuel cell modules in whole are disposed inside acasing to be securely held with each other.
 27. Solid oxide fuel cellbundled modules comprising: plural units of solid oxide fuel cellmodules disposed with an interval provided therebetween, and in such away as to be plane parallel with each other, said solid oxide fuel cellmodule comprising; a substrate with an internal fuel flow part providedtherein, at least a face thereof, in contact with cells, andinterconnectors, being an insulator; a plurality of the cells eachcomprised of an anode, an electrolyte, and a cathode, stacked insequence, formed on a surface of the substrate; and the interconnectorseach electrically connecting in series the cells adjacent to each other,wherein the respective cells are varied in area along the direction offuel flow, two modules at both the extreme ends, respectively, amongsaid plural units of the solid oxide fuel cell modules, being providedwith an opening, on one-side faces thereof, on the fuel inlet sidethereof, while the respective modules between the two modules at boththe extreme ends, respectively, being provided an opening, on both-sidefaces thereof, on the fuel inlet side thereof, and an interval retaininghollow member having a skirting part matching the respective openingsadjacent thereto being interposed between the adjacent openings, whereinthe solid oxide fuel cell modules in whole are disposed inside a casingto be securely held with each other, and are structured such thatpressure loss occurs at parts of the respective modules, where fuelinside the respective modules is released to outside.
 28. Solid oxidefuel cell bundled modules according to claim 20, wherein the cells ofthe respective solid oxide fuel cell modules to be coupled up are variedin area along the direction of the fuel flow on a module unit basis. 29.Solid oxide fuel cell bundled modules according to claim 20, wherein theopenings of the respective modules are securely held with the intervalretaining hollow member having the skirting part matching the respectiveopenings, or the interval retaining unhollow member having the skirtingpart matching the respective openings by sintering.
 30. Solid oxide fuelcell bundled modules according to claim 24, wherein upon disposing thesolid oxide fuel cell modules in whole inside the casing, an elasticmember is interposed between either or both of the respective modules atboth the extreme ends, and the inner wall of the casing.
 31. Solid oxidefuel cell bundled modules according to claim 20, wherein the substratewith the internal fuel flow part provided therein, at least the facethereof, in contact with the cells, and the interconnectors, being theinsulator, is a substrate polygonal, elliptical, or tubular incross-sectional shape.
 32. Solid oxide fuel cell bundled modulesaccording to claim 20, wherein a conductor leading from the anode at theforefront, or the rearmost in the direction of the fuel flow, and aconductor leading from the cathode at the rearmost or the forefront inthe direction of the fuel flow are transferred from the anode side of aninsulator substrate to the internal fuel flow part side of the insulatorsubstrate, thereby drawing out electric power from a fuel flow path sidethereof.
 33. Solid oxide fuel cell bundled modules according to claim32, wherein the conductor leading from the anode at the forefront, orthe rearmost in the direction of the fuel flow, and the conductorleading from the cathode at the rearmost or the forefront in thedirection of the fuel flow are disposed through the intermediary of aninterval retaining member.
 34. Solid oxide fuel cell bundled modulesaccording to claim 33, wherein the interval retaining member is aninterval retaining member made of an electroconductive material. 35.Solid oxide fuel cell bundled modules according to claim 33, wherein theinterval retaining member is an interval retaining member with thesurface thereof, plated with an electroconductive metal including Ag,and Pt.
 36. Solid oxide fuel cell bundled modules according to claim 33,wherein the interval retaining member is an interval retaining member,the constituent material thereof, containing an electroconductive metalincluding Ag, and Pt.
 37. Solid oxide fuel cell bundled modulesaccording to claim 20, wherein the substrate with the internal fuel flowpart provided therein, at least the face thereof, in contact with thecells, and the interconnectors, being the insulator, is a substrate withNi diffused therein.
 38. Solid oxide fuel cell bundled modules accordingto claim 37, wherein an amount of the Ni diffused corresponds to notmore than 35 vol. %.
 39. Solid oxide fuel cell bundled modules accordingto claim 20, wherein the constituent material of the substrate with theinternal fuel flow part provided therein, at least the face thereof, incontact with the cells, and the interconnectors, being the insulator, ismaterial composed of (1) a mixture of MgO, and MgAl₂O₄, or (2) azirconia based oxide, or a mixture of the zirconia based oxide, MgO, andMgAl₂O₄.
 40. Solid oxide fuel cell bundled modules according to claim39, wherein the mixture of MgO, and MgAl₂O₄ is a mixture of MgO, andMgAl₂O₄, containing 20 to 70 vol. % of MgO.
 41. Solid oxide fuel cellbundled modules according to claim 20, wherein the constituent materialof the interconnector connecting the anode to the cathode between therespective cells adjacent to each other is material composed mainly ofan oxide expressed by chemical formula (Ln, A) CrO₃ (in chemicalformula, Ln refers to lanthanoids, and A refers to Ba, Ca, Mg, or Sr).42. Solid oxide fuel cell bundled modules according to claim 20, whereinthe constituent material of the interconnector connecting the anode tothe cathode between the respective cells adjacent to each other is anoxide material containing Ti.
 43. Solid oxide fuel cell bundled modulesaccording to claim 42, wherein the oxide material containing Ti is MTiO₃(in chemical formula, M refers to at least one element selected from thegroup consisting of Ba, Ca, Pb, Bi, Cu, Sr, La, Li, and Ce).
 44. Solidoxide fuel cell bundled modules according to claim 20, wherein theconstituent material of the interconnector connecting the anode to thecathode between the respective cells adjacent to each other is materialcomposed mainly of Ag.
 45. Solid oxide fuel cell bundled modulesaccording to claim 44, wherein the material composed mainly of Ag ismaterial composed of one substance or not less than two substances,selected from the group consisting of Ag, Ag solder, and a mixture of Agand glass.
 46. Solid oxide fuel cell bundled modules according to claim20, wherein the constituent material of the interconnector connectingthe anode to the cathode between the respective cells adjacent to eachother is material composed mainly of Ag, and the interconnector iscovered with glass.
 47. Solid oxide fuel cell bundled modules accordingto claim 20, wherein the constituent material of the interconnectorconnecting the anode to the cathode between the respective cellsadjacent to each other is material composed of two kinds of materials,that is, a material expressed by chemical formula (La_(1-x)Sr_(x)) CrO₃(in chemical formula, x=0 to 0.6) deposited on a metal.
 48. Solid oxidefuel cell bundled modules according to claim 20, wherein the constituentmaterial of the interconnector connecting the anode to the cathodebetween the respective cells adjacent to each other is material composedof two kinds of materials, that is, a material expressed by chemicalformula (La_(1-x)Sr_(x)) CrO₃ (in chemical formula, x=0 to 0.6)deposited on a material composed mainly of Ag.
 49. Solid oxide fuel cellbundled modules according to claim 20, further comprising an interfacelayer between the electrolyte, and the cathode.